System for cooling conductive members



2, 1954 R. H. RHEAUME 2,693,347

SYSTEM FOR COOLING CONDUCTIVE MEMBERS Filed Nov. 29, 1951 INVENTOR RAYMOND H. RHEAUME W6 /?7AM ATTORNE United States Patent SYSTEMFFOR COOIJINGCONDUCTTVEFMEMBERS Raymondi 1H. tRheaume, Stamford, lzConm, assignor. l to Machlett -=Laboratories, rlncorporated, "Springdale,

GonrL, a corporation. of iConnecticut 1 Application {November :29, 19.5.1, .Serial No 253,926

.5 Claims. ((Cl. 2571250) .1Thisrinvention:relates- .to :a system; for-cooling conductivesurfaccscof electronttuhes. t'In-particulanit concerns -=atsystem"for-efficientlyidirectingthe;flow -of.a-.coolant,ov.er .the :external surface: of ganz-electron tube anode.

.JIll has become:commouapractice to :cool extcrnalanodcs ofrelectron tubes a with: relatively large volumes :of water .or other. liquid; coolants: having: high'iheat-storage;capacity. lncreasedrcooling has been achieved by. cutting grooves into the external surface 'of.;the :anode or adding fins ;to theranode surface, thereby increasing ithe :cooling' area. lu -some instances the ifins :or grooves have been 1 made spiral in an effort to increase the circulation of: the coolant, thus increasing efliciency. These expedientsihave almost reachedthelimit 'of their effectiveness. Almore efiicient means of cooling has "been needed for tubes of higher power level in. order toavoid materially 1 increasing anode sizes with consequent increases in .tubesizes.

My invention provides an elficient compact structure for-cooling a-conductive electron tube,surface, such as the externz'rlsurfaceof the anode. The-essential parts of my structure consistof a bafile means which is close spaced-to the surface to-be cooled and a plurality of walls or wall-l'ike members defining channels. These walls are not cooling'fins and, infact, are -advantageouslyafiixe'd to the batfle member rather thanto the anode. "The walls in-my preferred structure are advantageously made to extend the full distance between baffle andanode. Thusythe walls may perform a spaeing function. When so used, they-permit very close spacingbet-ween anode and baffle while at the same-time-avoiding contact between 'thesemembersat'anypoint. jln fact,it-is possible to obtain-uniform;spacing-at 'all points between the surface to be cooled and the bafilemsing the walls as spacing means.

"Thepassage' permitting flow-of coolant past the surface to be cooled is keptsmall by the close spacing between the brittle and the surface to be "cooled. 'The. small A passageproduces .a relatively large velocity of flow at'any given pressure of coolant. Close spacing avoids laminar flow, wherein the layer of coolant midway between the .an'ode'and, the jacket walhmovesmore rapidly than the layer adjacentthe anode. Intact; all of-theflow past the surface to'be cooled is'at the-same rate and is suffliciently close to'sa'id surfaceto actively aid inthe cooling. Likewise, close-spacing leaves'insuflicient room between anode *andb'afileforeddy currents to beset up. Thus, despite the fact that a smaller total volume of water is 'used than in the prior art, almost all of the water molecules which "flow past the=surface contribute toits. cooling.

' The efiicient use of thercoolant in -my: cooling system is assuredby turhulence,-;the.constant redistribution :of :molecules within-thezbodyyof.the coolant. ,Turbulenceis :a lay-product of high velocity. Tortuous channels "-be- :tween :the walls willralso-ltend to .produce turbulence. Where thesurface tozbe cooled gets hotter-than the boil- .ing point'of coolant,.turbulence is particularlyimportant. Where there: is .no redistribution of molecules, a microscopic layer of coolant immediately adiacent the ,area to be .cooled. is. transformed intoan. insulating layer of, steam. In addition .to the inefiic'ient ,cooling resulting. :from this insulation of coolant fromthe area to be.,cooled,1 boiling at thesurface to be :cooled may produce scaleand; in

fact, mavresultin highly destructive mechanical vibrations. The effect of turbulence is constantlyto remove {heated molecules of coolantfrom'the'layer adiacent the surface to.be cooled, and to substitute cooler molecules of "coolant.

2,693,347 Patented Nov. 2 1954 'rAlthoughtheamonnt of turbulence'islargely-dependent upon velocity, his not advisable \to 5 indefinitely .decrease passage ':size in an etfortto. increase velocity. If the stream dfipth (between the surfacexto-be cooled and-a ,ba'flie memberiis decreased until the super-heated layer adlacent'gthesurface isno-longer a'negligible part of the total depth,*turbulence will'cease and the flow will become "laminar. Accordingly, it is advantageous to keep the surface to be cooled spacedtfrom the baffie at all points bythe use of walls as 'previously described. In.fac t,-the baflle and the surface maybe spaced by the channel walls so thattheir spacingis optimum for maximum velocityof flow. and maximumturbulence everywhere over-the area tofbe cooled.

Water, the =mostfrequently used liquid :coolant,., is usually, available at relatively :lowpressures. In order to .increasethis pressure, additional. equipment, which is-sub- .ject 'to failure,'is'needed. Hence, in most instances, it .is advisable to avoid high; pressuresystems. 1 Bythe. same token, it is advisable to take full advantage of the pressureavailable by. obtaining a maximum velocity-flow over thejsurface *to'bencooled. -This. is accomplished in my invention by keeping small the passages through which the coolant passes.

By use-of my invention a-relatively highvelocity-stream is maintained at uniformvelocity over the whole area to becooledbecause {of uniformity in' the size of ,the coolant passage. In rny'preferred construction the :spacingbetweenteachpairxof'walls-is made uniform over the .whole length of zthe.-wa'lls. Thus. shallow paths highly uniform in cross section'aharea throughout-their length .are provided'so that the :coolant pressure will produce high velocitystreams'havinguniform velocity over 'thexwhole .areatobe cooled.

In "my invention the "walls are advantageously aflixed .tothebaffie plate in order that the-surface to be cooled may'ibemaintainedsmoothramd easily cleaned and-in order-that electrontubes maybe :replaced without replacingthebaflie and'the channel-walls. Thus'the tube is not complicated by the 'addition'of vanes tothe; outer surface-of its external anode. The-channel walls affixed to theibafile;also.;provide -aself positioning means which assures quick but highly accurate positioning of the baffle with respect to the surface to be cooled.

*In electron tubes .aparticular problem arises-Which calls-for solution by the. use of a specially designed, cooling system. This problem concerns the tendency for alternate'stripes of heat and relative absence ofyheat to occur along-the anode surface. It "has been foundthat by makingthe anode wall extremely thick theincreased conductive-eifectwill smooth out thegra'dient between the stripes. "However, it is costly ,to'make'thick anodes,

" tltisymyzpurpose to provide spiral paths .or channels-for the ,coolantsothat every channel will crosssome hot stripe. Thus the coolant contained. in each, channel will z share-nearly'equally in-the coolingofxthe hottest parts of the anode. Furthermore, the spiral walls will providea tortuouspath which will ten'd'to increaset urbu- "lence, hencethecooling effect of the coolant.

g'For-abetter understanding of my invention a more de- *ta'ile'd discussion-of one of its preferred embodiments" is included. This preferred embodiment concerns the coolingof avacuum tube anode towhich reference'is made i-in'the'following'drawings:

Fig. l 'illustratesinpartialsection;an-electron tube having, an external anode which is Positioned within the cooling'meansof-my invention.

Fig; 2 'illustrates-iin section the cooling means shown-in '{Fig's 'l' without-atube therein.

Fig. 3 illustrates in elevation this same cooling means from above.

Referring to Figures 1, 2 and 3, a cylindrical or tubular baffle member is employed to direct the flow of coolant along the outer surface of cup-like anode 11. A plurality of helical walls 12 are arranged between anode 11 and baflle 10. These walls are preferably everywhere uniform in size and shape and may conveniently be made of wire. They are advantageosuly permanently affixed to the inside of bafile member 10, as by'soft soldering, so that the distance between any adjacent pair of walls remains constant throughout their length. These walls are also advantageously made so that the anode, as well as the baffle member, is in contact with them substantially throughout its length.

The electron tube illustrated in Fig. 1 has an internal construction wherein are located an elongated free-hung filament 13 and a grid. The grid is composed of paral lel struts 14 circularly arranged and terminated at their base in cap member 15. The active grid structure is provided by a helical winding 16 advantageously made of non-emissive material. These electrodes lie coaxially within the'anode cup 11. Tubular member 17 is aflixed to the lip of the anode cup 11 in such a way that it is effectively folded back over said cup, thereby forming a reentrant portion to said anode. Adjacent the opposite end of member 17 annular anode terminal ring 18 is placed. The grid is mounted on an annular grid ring 20 parallel to the anode terminal, and the filament is supported on members aflixed to planar, circular filament terminals 21 and 22 at one end of the tube. The filament terminals are separated by a column composed of two Kovar rings 23 and 24 sealed to glass ring 25. A similar column separates cathode terminal 21 and grid terminal 20, namely Kovar collars 26 and 27 sealed to glass ring 28. The anode and the grid terminal rings are likewise separated by such a column having laarger diameter Kovar rings 30 and 31 separated by large bowed glass member 32. The ring 31) may be made in two pieces flanged at the junction 33 at which is made the final seal as described in the application of George J. Agule, Serial No. 118,878. An exhaust tubulation 34 may be ported through the bottom of the anode 11. A cap 35 may be provided to cover and protect the tubulation. The tube structure, as a whole, thus briefly described, is also described in the application Serial No. 185,645 of George J. Agule.

The battle 10 is the most important single part of the water jacket shown in Figs. 2 and 3. Water jackets may also be designed to cooperate with tubes of many shapes. Conformance of the baffie to the shape of the surface to be cooled is important in order to maintain the shallow stream required for high velocity. In this instance, the bafiie extends into the reentrant portion of the anode formed by members 11 and 17 in order to parallel the surface to be cooled throughout its length. At its other end, baffle member 10 is afiixed by means of radial flange 38 to a reduced diameter tubular member 37, which advantageously surrounds the cap 35 on exhaust duct 34. Tubular member 39 coaxially surrounds tubular member 37 to which it is joined at one end by radial member 43 which extends between the two tubular members and forms the bottom of an annular trough through which are made several holes 41. From the other end of tubular member 39 extends a short radially outward extending flange 42 to which is joined one end of tubular member 43 which is coaxial with and close spaced to baffle 10. As shown, it is possible to fabricate a single piece to provide all the members between baffle 10 and tubular member 43. The water jacket may be made an integral part of the tube as shown in Fig. 1 by soldering the other end of tubular member 43 to the adjacent end of anode member 17.

The use of a grid structure of the type shown in the tube of Fig. 1 produces some focusing of the electrons as they pass between the various grid supports 14 on the way to the anode. Thus the electrons will tend to bombard the anode in stripes around the anode thereby producing relatively hot stripes on the anode. This striping effect complicates the problem of adequately cooling the anode surface. However, if the coolant moved directly upward between the baffie and the anode in a direction parallel to the axis of the tube, the cooling effect of parallel streams of the water would be difierent. Accordingly, the preferred form of my invention employs spirals so that each stream of coolant will be equally as effective in cooling the anode. In other words, the spiral channels formed by the spiral walls cause the coolant to cross alternately the hot and cold stripes on the anode. In order that each of these channels cross at least one stripe, I propose to use a pitch in the spiral such that each spiral crosses at least one hot stripe over the length of the anode. Otherwise expressed, I arranged the helical walls so that each of them will have a minimum pitch, in revolutions for a total length of anode surface, equal to the reciprocal of the number of hot stripes around the cylindrical surface. It is usually advisable to use a pitch equal to something less than a full turn per total length, although in some instances several turns per total length will not slow the stream too much, due to back pressure.

The functioning of the water jacket is basically quite simple. The integral jacket may be made to fit a socket from which coolant is forced upward through tubular member 37 around the cap 35 on the exhaust tubulation. Thence the water moving upward takes the plurality of spiral channels formed by the walls 12 between the baffle 10 and the anode 11. Upon reaching the top of baflle 11, the coolant assumes a downward path between the outside of baffle 10 and anode member 17. This path continues on down between baflle 10 and tubular member 43, whence it flows into the channel formed by tubular members 39 and 37 and radial member 40. Thereafter, the coolant passes out through holes 41. Other means of access to and egress from the space between baflle 10 and anode 11 are possible and may be necessary with modified tube designs.

It is the purpose of the channels between the baffle and the anode to produce a high velocity stream of water adjacent the surface to be cooled. The high velocity is occasioned by minimizing the spacing between the anode and the baflle member. It is possible to successfully minimize this spacing because the wall-like members 12 act as spacers which keep the anode and the baffle everywhere separated. Thus, it is not possible for some portion of the anode to be inadequately cooled. due to insufficient flow of coolant over its surface where it is immediately next to or touching the baffle due to some eccentricity of its positioning. The reduction in this spacing reduces the area through which the coolant is able to flow. Since the velocity of the coolant is inversely proportional to the cross-sectional area of the channel through which it passes, the great reduction in the area of the channel afforded by my construction will permit a great increase in the velocity of the coolant stream. Since the rate of cooling is directly proportional to the .8 power of the velocity, this increase in velocity represents a material increase in the rate of cooling of the anode sufrace. It is my object to attain as high a stream velocity as possible by reducing the cross-sectional area of the stream path, specifically by reducing the distance between baffle and anode, wi hout reducing this area to the oint where turbulence will no lon er occur or where efficiency is lost due to excessive friction.

In order to achieve uniform cooling over all the surface of the anode, not only is the depth of the channel maintained constant, but the spacing between the walls is also advantageously kept constant throughout their lengths so that the velocity of coolant in any given channel will remain constant throughout the whole length of that channel.

Several features of novelty are included in the preferred construction of my invention as described. It is not necessaw that all of the novel features be used in coniunction with one another. Many advantages may be derived from use of one or more of these features without the others.

In the preferred form of my invention. the surface to be cooled is cylindrical. The shape of the channel walls may vary, but their use is essentially the same. In fact, should a complicated surface be chosen for cooling, the spacing function of my wall would prove invaluable.

I claim:

1. A system for cooling a cylindrical surface of a conductive electron tube member, said system comprising cylindrical baffle means uniformly spaced at all points from the cylindrical surface, a plurality of helical walls having a common axis and the same pitch and direction and located between the surface and the baffle and in contact with both, and means of access to and means of egress from the channels between the helical walls for the introduction and removal of a coolant.

2. A system for cooling a cylindrical surface of a conductive electron tube member, said 'system comprising cylindrical baffle means uniformly spaced at all points from the cylindrical surface, a plurality of helical walls fixed to the baffle means and contacting the cylindrical surface along the full length of said surface and means of access to and means of egress from the channels between the helical walls for the introduction and removal of a coolant.

3. A system for cooling a cylindrical surface of a conductive electron tube member, said system comprising cylindrical baffle means uniformly spaced at all points from the cylindrical surface, a plurality of helical walls having a common axis and the same pitch and direction, no wall making more than one revolution over the length of the cylindrical surface, said Walls being located between the surface and the baflle and in contact with both, and means of access to and means of egress from the channels between the helical walls for the introduction and removal of the coolant.

4. A system for cooling a cylindrical surface of a conductive electron tube member, in which conductive surface there appear a plurality of alternate stripes of relatively hot and cold areas running generally parallel to the axis of the tube, said system comprising cylindrical baflle means uniformly spaced at all points from the cylindrical surface and a plurality of helical walls all of which have the same pitch and direction, each wall making a turn over the length of the anode of at least that part of a revolution represented by the reciprocal of the numher of hot stripes, said helical walls being located between the surface and the baflle and in contact with both, and means of access to and means of egress from the channels between the helical walls for the introduction and removal of a coolant.

5. A system for cooling a cylindrical surface of a conductive electron tube member, said system comprising cylindrical bafile means uniformly spaced at all points from the cylindrical surface, a plurality of helical walls consisting of wire members of uniform diameter aifixed to the baflle means and contacting the cylindrical surface along the full length of said surface and means of access to and egress from the channels between the helical walls for the introduction and removal of a coolant.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,978,424 Gebhard Oct. 30, 1934 2,235,669 Conklin et al Mar. 18, 1941 2,317,442 Chevigny Apr. 27, 1943 2,512,373 Pakala et al June 20, 1950 

